The effect of prostaglandins, catecholamines, and adrenergic receptors in the modulation of the diurnal patterns of spontaneous uterine activity and of the diurnal variations of the dynamics of the pregnant uterus on uterine blood flow and maternal blood pressure will be evaluated in monkeys. Chronically implanted sensors will continuously monitor intrauterine pressure, uterine blood flow, arterial and venous blood pressures, and body temperature. Electronic integration and computer analysis of measured parameters will facilitate evaluation of the studies. These experiments are designed to elucidate some of the factors involved in the physiology and control of myometrial contractility and uterine blood flow and their influence upon current concepts of steady states, uterine blood flow and fetal homeostasis. A primate breeding colony will be maintained.